Process flow material (ores, fluids, gases, discrete parts, electrical power, and/or information) through process equipment by various and changing routes. This meaning of route, as a specific equipment set, is hereafter termed a path.
The particular path that is exercised in any given instance can depend on many factors: product type, equipment availability, equipment contents, transfer volume, process operations in progress, etc. Often a given transfer/movement may exercise one route on one occasion, and a different one at another time.
The most preferable way for a process operator (for purposes of this document "operator" and "control procedure" are synonymous) to select a transfer path is to tell the control system the nature of a path, for example the origin and the destination of the transfer, then let the control system determine the particular equipment resources which can, and are available to, effect the transfer. Subsequently the operator would prefer to operate the selected path as an entity by simple invocations, provoking the control system to perform the appropriate sequence of equipment operations (valving, switching, etc.).
While this is a preferable operating scenario, it is not simply done. The details of just selecting a path may consist of a very simple decision rule or a very complicated one. Performing the array of coordinated equipment operations of a path is equally complex.